themotoworks
Been Around the Block
continuing on the efi conversion topic, I finished that engine, I'll try to remind myself to refresh that thread with all the info... but I've been spending the last couple months modifying the heads, I took my first ducati build to loudon to get my racing license and loved it but it really made me want an even lighter and more powerful bike, the one I took dyno'd at 75hp and weighed 330lb, so I feel like I could get a lot more power from that engine.
I talked to bruce meyers who has been building these engines since they came out, and he gave me a lot of good info, most of the power gains come from the intake port, cam and bigger valves, he even reangles his valves slightly so the larger valves don't hit on overlap. I couldn't wrap my head around reangling the valves without changing the angle of the rocker pairs, and how that would actually work without changing the running clearance of the opener and closer during rotation, so I chose to run standard valves. I couldn't get my hands on a racing cam, apparently no one makes these anymore unless you order a batch, then you're still calling a place in australia and trying to convince them you're the real deal, so I gave up on that and bought an st-2 parts motor for a couple hundred bucks and swapped in the st-2 cam. from what I read, it's a good mild race cam when used in the 900ss.
to modify the ports, I milled out parts of the head and welded in inserts, then welded and blended the ports to the original head, I aimed for a wider intake port at the mouth, with a good taper to the valve seat, this should increase port velocity and take advantage of the greater overlap in the st-2 cam, these motors really fall on their ass above 7000 rpm.
after all the welding and stuff, I had to re-heat treat the heads because they lost all their temper in some sections, namely around the seats, which wouldn't be good, so I found a kiln on craigslist for cheap, fixed it up, and ran a t-6 solution, then aged, seemed to work fine. the heads were also pretty warped after that process, so I remachined the head sealing surface and re-reamed the rocker pin holes, it assembled fine, the cam bearing caps were quite tight but they still went in, so I say send it, let's see what it does.
I talked to bruce meyers who has been building these engines since they came out, and he gave me a lot of good info, most of the power gains come from the intake port, cam and bigger valves, he even reangles his valves slightly so the larger valves don't hit on overlap. I couldn't wrap my head around reangling the valves without changing the angle of the rocker pairs, and how that would actually work without changing the running clearance of the opener and closer during rotation, so I chose to run standard valves. I couldn't get my hands on a racing cam, apparently no one makes these anymore unless you order a batch, then you're still calling a place in australia and trying to convince them you're the real deal, so I gave up on that and bought an st-2 parts motor for a couple hundred bucks and swapped in the st-2 cam. from what I read, it's a good mild race cam when used in the 900ss.
to modify the ports, I milled out parts of the head and welded in inserts, then welded and blended the ports to the original head, I aimed for a wider intake port at the mouth, with a good taper to the valve seat, this should increase port velocity and take advantage of the greater overlap in the st-2 cam, these motors really fall on their ass above 7000 rpm.
after all the welding and stuff, I had to re-heat treat the heads because they lost all their temper in some sections, namely around the seats, which wouldn't be good, so I found a kiln on craigslist for cheap, fixed it up, and ran a t-6 solution, then aged, seemed to work fine. the heads were also pretty warped after that process, so I remachined the head sealing surface and re-reamed the rocker pin holes, it assembled fine, the cam bearing caps were quite tight but they still went in, so I say send it, let's see what it does.